Electrical heater



July 19, 1932. E. R. EVANS ELEGTRCAL HEATER Filed D60. 11, 1930 IWI Patented v`lilly 19, 1932 PATENT OFFICE EARL B. EVANS, F WASHINGTON, DISTRICT 0F COLUMBIA ELECTRICAL HEATER Application led December 11, 1930. Serial No. 501,781.

My invention relates to electrical heaters of the induction type embodying a metallic heat-radiating structure and a magnetizable core member linked therewith to generate large heating currents therein, at a safe or ne ligibly small potential.

ne object of my invention is to provide a heater of this type having Huid-circulating means, such as a fan, driven by motor means including the core member whereby the expense and complication of a separate motor and heater element are obviated.

Another object of my invention is to pro-V vide an electrical air heater with improved air-circulating means, includin motor means of the alternating-current, sha ing-pole type without any commutator, slip rings or armature windings. ,t

A further object of my invention is to improve the character and arrangement of the heat-radiating structure, particularly with reference to localizing the highly heated portions at points removed from the core member.

Other objects and advantages of. my invention will a pear from the followin detailed descriptlon of the embodiment t ereof shown in the accompanying drawing, wherein Fig. 1 is a plan view of a portion of an air or space heater, the heat-radiating plates being omitted for the sake of clearance;

Fig. 2 is a side elevational view of the heater shown in Fig. 1, the 4:front wall of 35 the casing bein broken away;

Fig. 3 is a similar view of the combined core member and motor to an enlarged scale;

Fig. 4 is a side elevational view of a modified form of heat-radiatingstructure; and

Fig. 5 is a detail view of a portion thereof.

Referringto Figs. l to 3 of the drawing, an air heater of the induction type particularly adapted for domestic heating purposes is shown. The heater comprises a box-like base 45 1, preferably'of sheet metal, provided with openings 2 for the admission of air below the heating element. The openings 2 may be formed by a punching operation whereby portions of the sheet-metal base are bent inwardly as shown in Fig. 2.

A stationary magnetizable core member 5 is arranged within the base 2 and is supported thereby in any desired manner. While this core member is shown as laminated, the laminations are rigidly clamped together to minimize the undesirable humming noise which results when the heater is energized by alternating current.

The core member 5 comprises a central leg 6, and two side legs 7 and 8, in the particular 60 embodiment shown. A primary windin 9, usually wound for 110 or 220 volts A. is disposed upon the leg 6 of the core member. v

The heater element per se comprises a plun rality of conductive elements linked with the core member 5 whereby large currents are induced therein to generate heat. In the embodiment shown in Figs. 1, 2, and 3, the heater element comprises a stack or series of thin plates 12 of copper or aluminum or allo s of 70 these metals, of example, whereby a arge radiating surface in proportion to the volume of mass of the heater element is obtained. Each plate 12 forms a short-circuited or single-turn secondary for the core member,l 5. The currents which flow in the respective plate members depend upon the total resistance r of the current path in each plate member and the number of plate members.

The plate members 1 2 are preferably of the 30 same dimensions to equalize the heating effect. The resistance lr of each' plate member is a function of the metal of which are plates are composed, the thickness of the plates and lengths and cross-sectional areas of the current paths in the plate members. The heat developed at any point in any of the plate members is proportional to the increment of resistance A1' at that point and the square of the current. In accordance with a further 9 feature of the invention, the resistance of the current path is varied at dii'erent points to localize the maximum heating ei'ect away from the core member 5 and where the Huid to be heated is at its highest temperature. l

This result may be accomplished by slotting the plate members 12 to restrict the current paths where it is desired to develop the greatest heat. Thus, a central slot 13 extending downwardly from the upper end of the 10 plat; members 12 and two side slots 14 may be lrovided. The slots 14v do not exten completely to the top of the plate but leave restricted current paths 15 preferably not greater in cross section than the current paths between the slots 14 and the sides of the plates. At the bottom, the slots 14 follow the outline of the plate members 12 and extend to the upper edge of the core member 5.

Where the plate members l2 are linked with the core member 5, it is desirable to minimize the heat developed but the space is limited and thus there is a definite limit to the possible enlargement of the plates at this point. However, by slotting the plates as indicated, the desired distribution of resistance, and of heat, may be approximated and the cross section of the current path may be a maximum adjacent the core member and a minimum at the upper end of the heater element where the' heated fluid emerges and is at its highest temperature.' Obviously the particular arrangement of slots shown, while advantageous, modified in accordance with the principles outlined above.

In accordance with a further feature of the invention, fluid-circulating means such las fan blades 20 are provided which are driven by the core member 5 and are operative to increase substantially lthe circulation of air through the heater. In the .embodiment shown, the fan blades 2O are formed in a disc member 21 pivotally supported on a shaft 22 and projecting into a slot cut into the core member 5. The slot does not extend through the entire side leg of the core member. Ad-

ditional fan blades 23 may also be mounted upon the shaft turn the disc member 21, a

In order to small auxiliary magnetizable core member 24 at the edge of the core member 5 and presenting pole pieces adjacent the slot in said main core member but tangentially-arranged withl respect to the disc member 21. The auxiliary core member 24 is ener 'zed by the winding 9 and, as it is not linke with the plate members 12, it is traversed by an alternating ux which is out of phase with that traversing the core member 5. The out-of-phase fluxes cutting the edgeof the conducting disc 21 produce a turning torque thereon as is well understood by those skilled in the art', this type of motor being usually referred to as the shading-pole type.

It will thusA be seen that the invention prov vides a combined fan and inductive heater of simple construction .and which has no commutator, slip rings, armature winding or similar element, thereby eliminating the noise and radio interference from that source, important considerations where the heater is employed for domestic heating purposes. Motors of this type have the further advantage for application to domestic heaters that is only illustrative and may be p they are normally of slow rotative speed and d hence are adapted to rotate the fan blades noiselessly at a relatively slow speed without any necessity for reducing gears.

In Figs. 4 and 5, I have shown a modified form of heater element adapted to be used in a heater of the type shown in Figs. 1-3. A core member 5a 1s energized by the primary winding 9a, as in Fig. 1. The heater element forming a low-resistance secondary around the core member comprises U-shaped metal block 26,- such as a cast brass or bronze block, machined to fit the core member snugly. Electrical insulation between the block and the core member is unnecessary but heat insulation may be employed if desired. The block 26 is hollowed out to receive the lower ends of metal wires or rods 27 which are preferably brazed or welded into the block 26. In order to localize the heating at the upper end of the heater element, the cross section of the wires 27 is reduced, as by flattening portions thereof and erforatin the deformed portions, as shown at 28. Ad itional cross wires 29 may be employed to increase the heat-radiating surface these wires being also provided with flattened portions 30, as shown in Fig. 5. The cross wires 29 may be brazed or welded to the wires 27 and the flattened portions may be staggered or inclined to the vertical or otherwise arran ed to provide a tortuous path for the air or uid circulated thereover.

Various other modifications may be made in the specific embodiments shown and described without departing from the scope of the invention as set forth in the appended claims.

I claim: l

1. Electrical heatin apparatus comprising a sheetmetal heatlng element provlded with passages therethrough, inductive means for generating currents in said element jto heat the same and a fan for circulatin fluid through said passages energized by t e inductive means.

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2. Electrical heating apparatus comprising a stationary metallic heating element of extended area. and provided with passages therethrough, means including a magnetizablecore member for inducing currents in said element to heat the same and a rotating member in cooperative relation tosaid heating element and affected by the magnetization of said core member.

3. Electrical heating apparatus comprising a stationary metallic heating element of y extended area, means including. a slotted magnetizable core member for inducing cur' rents in said element to heat the same and fluid-circulating means including a pivoted disc extending into the slot in said lcore member.

4. Electrical heating apparatus comprising a magnetizable core member, a stationi ary lamellar vmetallic heating element havculating means embodying a pivoted armature member arranged* adjacent lsaid core member to be affected by the magnetization thereof.

6. Electrical heating apparatus comprising a stationary lamellar heating element of extended area, means including a magnetizable core member for inducing heating currents therein and fluid-circulating means therefor actuated by said core member.

l7. An electrical air-heater comprising a series of conductive elements having a large ratio of surface area to volume and defining a series of air-flow channels, means for causing current to traverse said elements to heat .the same and means for circulating air through the heater, said last-named means including motor means of the shading-pole type.

8. An electrical air-heater comprising 'a alternating-current winding on said core member and air-circulating means includin a fan 4disposed adjacent said channels, sai air-circulating means being combined with said core member to rotate said fan in accordance with the energization of said windlng. t

12. An electrical air-heater comprising a stationa metallic heat-radiating element havin a arge ratio of area to volume, means inclu lng a conductor electrically insulated therefromfor heating said heat-radiating elcment, a fan directed upon said heat-radiating element and motor means of the shading-pole type for rotating said fan.

13. An electrical air-heater comprising a metallic heater element, a fan disposed below said element and arranged to direct air thereon, a pivoted disc connected to the fan blades to rotate therewith and means for inducing heating currents in said heater element andl constituting a shading pole adjacent said disc to exert a turning torque thereon, said means includin an energizing winding electrically insulated; from the heater element.

In testimony whereof I aiix my signature.

' EARL R. EVANS.

series of verticall disposed conductive plates spaced apart to eine vertical air-flow channels, means for causing current to traverse said plates to heat the same and means for circu ating air through said vertical channels, said last-named means including motor means of the shading-pole type.

9. An electrical air-heater comprising a series'of vertically disposed conductive plates spaced apart to deline vertical air-flow channels, means for vcauisng current to traverse said lates to heat the same, motor means of the s ading-pole type and embodying a pivoted rotor of conducting material dis osed below said plates and fan blades com ined` with said rotor and arran ed to augment the circulation of air throug saidvertical airow channels.

10. An electrical air-heater comprising a series of conductive plates spaced apart to define parallel air-flow channels, a magnetizable core member linked with said plates, an alternating-current winding on said core member, a fan for circulating air through said channels and means for rotating said fan including a rotor element and means for inducing out-of-phase currents therein to produce a turning torque thereon. u

' 11. An electrical air-heater comprising a series of conductive plates Aspaced apart to define parallel air-flow channels, a magnetizable core member linked with said plates, an

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